A reflective liquid crystal display device performs a display reflecting incident lights from surroundings using a light reflector. Since the display liquid crystal display device is constant in a contrast ratio regardless of luminosity of the surroundings, it shows a favorable display under comparatively light environments from direct sunlight to a room inside. Since a transmissive liquid crystal display device performs a display making a backlight light as a light source, it shows a favorable display under comparatively dark environments from direct sunlight to a room inside. Since a transflective liquid crystal display device equipped with both of a reflective electrode and transparent electrode within one pixel and equipped with a backlight light source, it shows a favorable display under a wide range of environments from direct sunlight to a room inside.
The transflective liquid crystal display device is configured to house a light reflector on an inner surface of a liquid crystal cell and stack one polarization plate and one or two phase plates at an upside and downside of the liquid crystal cell. Focusing attention on a reflective display unit since the unit uses only one polarization plate, the configuration is called a single polarization plate display system. Since the system performs a display utilizing a change of phase differences of a liquid crystal layer, it has characteristics that a contrast ratio is excellent and a driving voltage is low.
In addition, in order to improve luminosity and obtain a higher quality display like paper by disposing of a mirror surface reflection, light scattering means are used. In the light scattering means there exist a light scattering plate having a concavity and convexity on a reflection surface, a diffusive adhesion consisting of not less than two kinds of transparent media with a different refractivity, and the like. Since the light scattering means have an effect of broadening light propagating directions, they can obtain a luminous reflective display even when an observer and light source, macroscopically seen, are not in a relation of positions for a display plane which satisfies a positive reflection condition.
In the single polarization plate display system there exist a normally closed type that performs a dark display in no voltage application and a luminous display in a voltage application; and a normally open type that performs the luminous display in no voltage application and the dark display in the voltage application. Most of conventional transflective liquid crystal display devices are the normally open type.